2" TOADLOADERS are compatable with 8" SCTs using
our exclusive docking adapter, see link above right

Weight: less than 2.5 lbs. (approx.)

Over the years, VSI has continually taken the best features of all our previous
focuser designs and incorporated them into new "super focuser" models. Just
one of many of these super features is our huge dual 2.5" diameter custom
machined "GUN" knobs incorporating lightweight polymer cores encased in thick
aluminum shells (see picture at left). These giant knobs are easy to grip
and rotate using minimal tactile pressure and resemble the rotating cylinder
on a revolver, thus the name "GUN
KNOBS." VSI products are continually improved to [also] leave
copy-cats in the dust. Of course, VSI knock-offs are the greatest form of
compliment! It tells you that VSI products
are always the best by design, function and application. The
only way to keep ahead of these imitators is to design new and creative focusers
faster than they can copy our designs and incorporate them into their product
lines. This unique design philosophy has pioneered our Crayford focuser
development since John Wall first invented it back in the early 1970's (see
"Brief History of the Crayford Focuser" below), and kept VSI on the
"bleeding-edge" of focuser design for decades.

VSI considers the most important mechanical feature
to be the dual pressure points on the Crayford rod. Instead
of one pressure point, which has been copied by every Crayford focuser
manufacturer, VSI now uses two identical Teflon pads with two large set screws
(see picture at right). This design upgrade literally doubles the pressure
applied to the Crayford shaft, in effect doubling the holding power. By applying
equal pressure along a full 1-inch length of the Crayford rod and the
entire 1-inch width of the moving tube's machined flat, you create a
more positive rack & pinion-like movement, while cutting your tactile
contact, necessary to move the focusing tube, in half.

Our
exclusive QUAD-LOCK [Zero-Flex] system
(pictured left with the focuser's moving tube extended to expose
the two additional locking set screws) offers astroimagers a rock-solid coupling
between a focuser's moving tube and the 2" barrel nose. Four tightening screws
lock the 2" barrel nose into the focuser's moving tube - two 10-32 Nylon
thumb screws and two [hidden] 8-32 set screws. The first two thumb screws,
opposed by 90 degrees, lock your barrel in place from one end of the tube,
and the other two set screws lock from the other end of the tube. This 4-screw
application allows any 2" barrel nose to meld with the focuser's moving tube,
creating a zero-flexure coupling under any load. See
Slider Adapters link for more info on VSI's exclusive adapters.

VSI's massive 2" TOADLOADERS are designed for astroimaging. So creating
a rock-solid coupling between the focuser's moving tube and your extended
imaging train is mandatory. As you know, 2" and 1.25" barrel nose formats
are the "weak link" between your focuser and long extended imaging trains.
These barrel nose formats are for eyepieces but, somehow, all standard focusers
have always been created to accept this [less than adequate] format - even
VSI focusers. Very seldom do you insert an eyepiece directly into a focuser,
unless you are using a Newt/Dob for visual observing. You [at least] have
a standard diagonal between your focuser and eyepiece, when using catadioptric
and refractor type scopes. Now you can convert a focuser's standard 2" barrel
nose format to solid, low-profile [industry-standard] threaded formats (2"-24tpi
threads, or standard 42mm-0.75mm thread pitch T-thread) with the simple use
of VSI adapters (item #A2LT &
#AT2 shown at right). Using VSI's exclusive QUAD-LOCK
ensures that the coupling is rock-solid so you can stack an extended, long
profile imaging train without flexure!

These two hidden [captive retaining] set
screws on the focuser's moving tube (pictured right) are also
designed to hold our Hexagonal 1 in the focuser. A specially grooved barrel
nose on the Hexagonal (see TURRETS link for details) allows you to freely
rotate the active eyepiece position to obtain a more comfortable viewing
position.

To further reduce noise and vibration, and better isolate the focusing
motor(s) from the focuser housing, the motor's drive shaft is [now] coupled
to the Crayford focusing shaft using precision Delrin spur gears.
VSI has switched from metal to Delrin spur gears because Delrin (an
indestructable polymer resin) is more durable and lasts longer than metal
gears. And, VSI uses only the best Delrin gears available, with brass insert
hubs and double metal set screws that lock the spur gears securely to the
motor and Crayford drive shafts.

The TOADLOADER's other standard features
include an outer housing that docks and locks to the rear of
your SCT's visual back utilizing the larger 3.25"-16tpi threaded format for
Meade, and an adapter ring (#AMC33, $99) for Celestron
3.29"-16tpi visual backs. This very important large format "lock & load"
docking totally eliminates flexure with even long, extended imaging trains.
Why do you think people like Dr. Frank Melsheimer of DFM, or John Stiles
of OGS are so emphatic about massive visual back assemblies, etc? Because
without a solid visual back, your pointing and tracking accuracy simply goes
away. This flexure is mainly due to the effects of gravity on your scope
as your pointing position changes over time. NOTE: John Stiles insisted
that my custom machined mounting plate (to dock a customer requested
focuser) on one of his 20" OGS Cassegrains was at least 12" in diameter
and 1/2" thick minimum (see User INSTALLATIONS link, Leeward Community College).

The perfect marriage (if there is such a thing) between focuser and rotator!
Combining the Zerotator and 2" ToadLoader
(pictured at right) creates a rock-solid, stable rotating platform
for astroimaging or just rotating your diagonal or Hexagonal to a more
comfortable viewing position. The caged needle bearing loaded Zerotator can
handle any load you stack on it, because it was designed to hold your entire
imaging train - focuser, optical manifold, CCD camera, etc., etc. And it
has a 2.75" internal clear aperture so vignetting is not a problem.

VSI TOADLOADERS utilize the famous "Crayford" design, which is world
renown for its zero-flexure, zero-backlash and simple mechanical qualities.
Unlike the other "Crayfords" on the market, that use a cylinder section to
hold their four bearings in place (they also claim being first to do so,
but this Crayford redesign was originally introduced by Paul Van Slyke and
copied by others, see S&T Feb 1986, P199 or go to
"Four-Speed 17.5" Newt" link for article re-print),
the TOADLOADER's housing is a complete cylinder with four 1" diameter [Crayford]
ball bearings secured to the housing on both sides of all the bearings
(patented), providing a much higher degree of stability and load handling
capability. Instead of using two bearings [supported by a frame] at each
end of the Crayford drive shaft to provide pressure on the moving tube, VSI's
Crayford design uses a single center pressure point on the rotating
drive shaft (supported with a pure virgin Teflon pad), which offers a fluid
surface so near-infinite force can be applied with no possible warpage of
the drive shaft (also copied by others). No positive focusing
action, like with R&P focusers, could be achieved - until now. The TOADLOADER
movement is not only as smooth as a 20 year-old, single-malt Scotch whiskey,
but the silky action is extremely positive and reactive to the slightest
touch.

VSI's
exclusive MICRO-DIAL (micrometer) ultra-fine
focusing capability provides this focuser with the finest
incremental focusing capability (by many factors) over any other focuser
on the market (see picture below right). One full rotation of the micrometer's
dial yields 0.00375" of travel with incremental indic interpolation that
is repeatable to (better than) an unbelievable
75/millionths of an inch. VSI's Micro-Dial in not just another
so-called fine focus control for visual observing like the ones offered on
almost every other focuser on Planet Earth. To call a Micro-Dial fine would
be like calling the space shuttle slow (17,500mph). Think thousands of times
finer than anyone else's so-called fine focus control. A lot of experienced
astroimagers, not familiar with VSI's relatively new Micro-Dial (with tactile
sensitivity beyond any other) think that it is impossible to obtain
critical focus without hands-off autofocus computer control. Not true! In
fact, computer focus control is not as accurate or fine as VSI's manual
Micro-Dial. Interpolation to better than 0.000075 inch. Do the math - indices
vs steps. But only if you want to focus manually, as all TOADLOADERS can
be equipped with temperature compensated autofocus so you can have the best
of both worlds - ultra-fine manual and autofocus capabilities.

And you disengage the TOADLOADER's motor
and/or engage the Micro-Dial with the turn of a knob. No dysfunctional [autofocus
only] motor locked shafts or, worse yet, knobless focusers! Oh, you wanted
to do some [analog] eyepiece observing too. Sorry, not can do! Did I mention
dysfunctional? What are they thinking? Not.

VSI TOADLOADERS are designed for the current
generation of Meade/Celestron Schmidt-Cassegrain telescopes (10" and
larger) that focus by moving their primary mirrors (which always
have an unacceptable amount of lateral image shift when focusing), and accept
accessories via their standardized threaded visual backs. However,
TOADLOADERS can also be used with any other type
of telescope using optional VSI screw-on or custom docking
adapters. Since 2" TOADLOADERS are specifically intended to
be secondary docking focusers, and work in conjunction with scopes that have
wide-range primary focusing mechanisms, the travel range is kept relatively
short (around 1"), but more than adequate for any focusing application. The
TOADLOADER's shorter focus travel is actually many times the amount required
to adjust and pin-point focus your SCT, because your primary focuser's large
focusing range can easily place the image at a "ballpark" point between the
secondary docking focuser's lesser range. Longer [moving tube] travel lengths
are available by special order.

Another exclusive VSI feature is the TOADLOADER's vibration dampening system.
Note the stainless steel motor arm (see picture at right). Stainless steel,
having a very high density, is the best material to dampen motor vibrations
when a motor must be in close proximity to the eyepiece, like focusing motors.
This undesirable vibration can easily transfer to what you see in your
telescope's eyepiece.

WARNING:
Be aware that all [so-called]
Crayford focusers, are not really Crayford focusers. Deceptive advertising
by many dealers, trying to take advantage of the Crayford's reputation, offer
Crayford-type,
Crayford-like or
Crayford-style focusers
that have very little to do with the true Crayford design. NO radial ball
bearings, NO zero-image-shift, NO fluid motion, NO ultra-tactile sensitive
control, NONE of the above functions that made the Crayford the finest precision
focuser on Planet Earth. These non-Crayford focusers typically use plastic
pads to simulate Crayford bearings and other inferior construction techniques
that diminish the Crayford name. Only a focuser that uses four radial ball
bearings can [rightfully] be called a Crayford focuser. -
PBVS

Also see Miniature Slot Car Bearings vs Large-Diameter
Precision Bearings section below for more info on this subject.

Focal Reducer "HIDDEN CAVITY" Super Feature

All models of Docking Focusers have our exclusive Focal Reducer "Hidden
Cavity" feature machined into the rear of their moving tubes. Just insert
your Celestron or Meade focal reducer into the back of your 2" TOADLOADER,
and your new, focal reduced profile has just been cut to zero. Then reinstall
your focuser, insert a standard 2" diagonal or VP Slider in your [focal reducer
equipped] 2" TOADLOADER and you're ready for super stable, efficient,
low-profile, wide-field operation.

You can also use this focal reduced configuration in your focuser mounted
on other [similar focal length] scopes, not just commercial Celestron/Meade
Schmidt-Cassegrains. Even if you don't use a focal reducer in your focuser's
hidden cavity, the larger internal diameter provides an ultra-wide clear
aperture that guarantees no vignetting, even with very fast scopes. Note
that the internals of the above focuser were intentionally NOT flat blackened
for demo purposes only.

This unique "hidden cavity" super feature has been around since the beginning
of VSI. Over two decades. You may remember the first VSI focusers called
Monster focusers, then named MasterGliders, and now called 2" TOADLOADERS
- 20 years plus is a long time! I changed the name because everyone and their
brother was calling everything "monster this" and "monster that," etc. In
fact, they still do. Maybe you remember my old "monster" display ads in
S&T, with the picture of a monster coming out of my focusers that was
a cross between "The Creature from the Black Lagoon" and a T-Rex? Now you
find that a "toad" has replaced the "monster."

FYI, if you are at all familiar with VSI, then you know that I like
to "march to a different drum." Honor, reputation and dignity are business
and marketing traits that are not always familiar to others.

Speaking of that, a relatively new focuser business, that seems to
be filtching more than just my ideas from others, has "borrowed" my design
and now features it in a small display ad in S&T's Market Place. Am I
ever bothered by these unethical copycat activities? No, because it is the
grandest form of flattery. A compliment that has no comparison. And it is
not even a true Crayford focuser, so that makes the theft even more
meaningless.

As I have mentioned before, Crayford-type, Crayford-style and
Crayford-like do not make a true [radial ball bearing] Crayford focuser,
and VSI's bearings are five times the size of others. It is an insult to
John Wall, the inventor of the Crayford focuser (see bottom of this web page),
to use the "Crayford" name to describe a pseudo-Crayford knock-off at best.
Besides, my unique products are never based on one or two features, like
others. As with all my products, they are based on an overall design concept
that is timeless - a build-quality that will endure far beyond your
lifetime.

Although I do have a couple of patents, this "cavity" is not one of
them. So rampant pilfering of many of my design features is an on-going activity.
Over the years, I have found that patents are not worth the initial expense
(i.e. attorney's fees, patent fees, maintenance fees for the life of the
patent, etc.). And you can literally go broke fighting patent infringements
through the courts. - PBVS

VSI's Exclusive Zenith Lift System

VSI's Zenith Lift System (patented), installed on all focusers, provides
a unique lift feature that balances focus control at the zenith, or
near zenith, observing/imaging positions. The Zenith Lift System (ZLS) was
created so the astroimager, or visual observer, can easily take advantage
of the more transparent overhead zenith arena. If balanced zenith lift
is not needed, you can easily remove the springs by slipping the hooked ends
over the Allen screws - instant gone!

FYI, this Zenith Lift System has nothing to do with backlash, as others
have wrongly assumed in their display ads. They are trying to discredit the
ZLS without even understanding its function. The more they try (desperately)
to "poo-poo" VSI products, the more they humiliate and embarrass themselves.
When will they learn that you can't destroy the reputation of a good product
with words, especially words that only reveal their own jealousy and ignorance.
A product can only destroy itself by its own actions. - PBVS

We all know that you are looking through about 100 miles of atmospheric
distortions on your horizon, but you are only observing through about 10
miles of atmosphere at your zenith. Obviously, you will obtain the best
astroimages and visual observations when your scope is pointing straight
up.

The mechanical apparatus comprises two heavy-lift springs (pictured at
right) that are attached between the focuser housing and the moving tube
on both sides of the focuser. Also, the TOADLOADER's mechanical spring-loaded
lift system will greatly assist your autofocus stepper motor and DC servo
motor when working around the zenith.

HINT: By setting your focus point further in, or further out, you
vary the amount of lift capability to better balance your focuser's load.
In other words, rack your focuser in most of the way, and you have light
lift for a lighter load. Rack your focuser out most of the way and you have
heavy lift for extended imaging trains. Just set your SCT's primary focus
at the inner, or outer, point of your secondary focuser travel for different
loads. Of course, if your load is light, and you're observing near the horizon
(say, in your neighbor's window) you don't need the mechanical lift springs.
Simply slip the springs over the Allen head screws to remove them.

Commercial 2" Focuser Size/Mass Comparisons

No words are really needed here, but do note the size of the Crayford
bearings, where applicable.

Miniature Slot Car Bearings vs Large-Diameter Precision
Bearings

A penny for your thoughts. These pictures illustrate the difference in size
between the bearings used in all other Crayford focusers (that I know of)
compared to the bearings in VSI focusers. What you can't see in the picture
is the lack of quality, but we'll get to that later.

Anyone can purchase these miniature slot car bearings on the internet
for about a dollar or two each in quantities of 10, as pictured above. Dealers
can purchase them for under $1 each in bulk quantities, so why do Crayford
focuser dealers [gladly] sell you a replacement bearing for $25? Ouch! I
hear that people need to replace them frequently. A VSI bearing has never
been replaced, ever! These slot car bearings are not even designed for loading.
They are designed for hi-speed rotation, usually around 20,000 to 80,000
rpm. Whoa! That's fast! That means that their tolerance has to be very low
to accommodate those extreme speeds. In other words, sloppy bearings designed
for speed, not precision. Slot car bearing static load is [at best] around
13 lbs. and their dynamic load handling is around 44 lbs. That rating is
for a precision bearing of the same comparable size because that is the only
reference I could find. Slot car bearings don't even list their load bearing
capacity, probably because they are way below the numbers that I referenced.
What do you want for a dollar?

As you can see, almost two of these miniature slot car bearings can be dropped,
side by side, through the center hole in a VSI bearing. VSI has always used
precision radial, chrome steel ball bearings in all focusers since day one
over 20 years ago. For simple comparison, each VSI bearing has a static load
capability of 310 lbs. (slot car = 13) with a dynamic load capability
of 740 lbs. (slot car = 44). That load rating is times four [bearings] when
it's on your focuser. And precision radial ball bearings have much tighter
tolerances because they are not designed for crazy hi-speed operation - a
few hundred to a few thousand rpm max.

What kind of rotational speeds are we talking about for a Crayford focuser?
Fractional, less than one rpm. So why use hi-speed, low tolerance bearings
in a Crayford focuser? Maybe you would say cost. The large precision
radial ball bearings I use are around $4 or $5 each. Not cheap, but not overly
expensive either. Maybe it looks better to hide the bearings inside the focuser's
housing? I would hide them too if they were that small. If the bearings were
hidden inside the housing, they could even buy cheaper open-race bearings
instead of shielded or sealed bearings. All VSI bearings are not just shielded,
they are sealed so zero contamination can get inside the bearing's race,
whether they are exposed to the elements, or not.

Another poor design on most Crayford focusers is their one-sided bearing
mounting, using a shoulder screw. This causes the bearing to flex from the
unsecured [screw-head] side of the bearing. VSI focusers use a 3/8" diameter
stainless steel (SS) pin that is secured by SS screws from both sides of
the bearing directly to the focuser's housing. This super secure bearing
mounting provides ultra-secure, zero flexure movement of the travel tube.
There are dozens of other reasons why VSI focusers are superior, expecially
in load handling, to all other Crayford focusers on the market. This is just
one more reason.

VSI's Dual Control Hand Paddle

Our Mega-Power Dual
Control hand paddle incorporates individual IN/OUT speed-torque control
for balanced load even at zenith positions. Just turn the knob below the
push button (see picture at right) to change the speed of the IN travel of
the DC Servo motor. Turn the other knob to control the OUT travel speed.

Other hand paddles have one knob to control both IN and OUT speed, so
when you are observing near the zenith and push the IN button, your motor
strains to lift the load at reduced speed and torque, and drops the load
at a much faster speed when you push the OUT button. With VSI hand paddles,
you can balance your load by simply adjusting the two individual speed control
knobs. Your IN/OUT speed can be precisely controlled for any load and any
observing elevation from horizon to zenith with a simple turn of a knob(s).

This new VSI circuit design instantly starts the rotation of the motor,
even at it's lowest speed, as soon as a button is pressed. No more time lag
between direction changes, like other hand paddles. This new paddle delivers
super-smooth, "analog" speed control that is mechanically and electronically
near-indestructible.

This paddle is used to control our DC servo motor only. It will not operate
the Lunatico stepper motor. Uses 120vac wall-wart type power supply (included
when ordering appropriate focuser package) or 12vdc car cigarette lighter
(optional). Operating voltage: 12 to 24vdc.

The Importance of Dual-Motor Controlled Focusers

VSI motorized focuser
models offer two types of motor control - DC servo and stepper. In
fact, VSI focusers offer the only dual-motor control on the planet (that
I know of), allowing both motor types of remote focusing control with a fast
and easy "slide-out/slide-in" motor switch-out (see picture at left). You
can also disengage either motor from the drive train for hands-on manual
focusing with the instantaneous turn of a knob.

Why does VSI offer these exclusive motor features? Because DC servo motors
are analog and introduce no vibration or noise into the drive train like
digital autofocus stepper motors, which are inherently noisy and cause step
vibration (even when microstepping). DC servo motor control offers smooth,
remote hands-off eyepiece focusing via the Dual Control hand paddle.

On the other hand, stepper motor control offers wonderful computer controlled
autofocus for astroimaging, but is not capable of vibration-free driving
of the moving tube, especially at resonant step frequencies, which cause
your star images to jump all over the place when attempting to focus, making
it impossible to remote eyepiece focus. This is why autofocus computer
subroutines stop focusing, take a focus image, then do it all over again
until perfect focus is achieved - a time consuming process, but acceptable.
Although remote push-button control is offered on autofocus electronic hardware
packages, via two push-buttons, you really can't use it for anything more
than repositioning the focuser's moving tube to begin autofocus computer
controlled focus procedures. It is simply a convenience feature. You can't
do simultaneous visual eyepiece focusing with a stepper motor because it
induces vibration when activated.

This little known motor control fact is very important when considering
the purchase of a focuser that you want to use for both visual, remote eyepiece
focusing and computer controlled astroimaging applications. You can't have
hands-off remote eyepiece focusing and computer-controlled autofocus for
astroimaging, unless you have a focuser with dual-motor control capability.
This is something that the other single-motor focusers on the market don't
want you to know, until it's too late. Unfortunately, this lesson is usually
learned the hard way. Even though this info, that you are reading now,
is buried [here] in this link, you may be one of the lucky ones, if you were
seriously considering a dual-purpose focuser for both remote visual focus
and computer-controlled astroimaging.

Re-Engineering & Improving the Basic Crayford
Design

Although most Crayford focusers on the market today utilize VSI's [original]
central pressure point design, we continue to stay ahead of the game by
continually improving our products, as noted by the myriad of improvements
to our TOADLOADERS. VSI has always maintained only the basic Crayford concept.
Everything else has been thrown out the astro-portal and redesigned from
the ground up. We have modified the four-bearing support platform by supporting
the bearings from both sides (a feature others have copied for many years
now), using hardened steel drill rod shafts and a complete cylinder instead
of a cylinder section, providing more than twice the stability compared to
single-end supported, bearing mounting systems. We have also made the entire
structure more massive, and increased the typical bearing size (approx. 1"
diameter bearings). The drive shaft support mechanism has also been re-engineered
to eliminate the weak, flimsy, distortion prone standard drive shaft mechanism
(see above diagrams) provided by many other manufacturers. The above left
diagram explains the internet reports of ball bearings literally exploding
due to over tightening a poorly designed drive rod tensioning mechanism.
If the two drive shaft bearings remain fixed perpendicular to the drive shaft,
while the shaft itself is allowed to warp [away from perpendicularity] from
over tightening, then the bearings will bind causing locking of the drive
shaft and danger of an exploding bearing. Even replacing the ball bearings
with bronze bushing-type bearings will not eliminate locking or pinching
of the drive shaft from normal tightening of the tension mechanism. Increasing
the diameter of the drive rod will relieve some of the warping, but it will
also give you a much coarser [ratio] movement of the tube, which is not
acceptable, at least at VSI.

To apply force at the center, instead of at the outer ends of the drive
shaft, VSI uses two expedient and economical virgin Teflon pads backed by
two adjustable, large Allen head set screws. Engineering studies have shown
that, in this application, center mounted Teflon pads provide an inexpensive
method to totally eliminate drive rod warpage and inherent concentric machining
errors while allowing the user to adjust and apply a much higher force between
the drive rod and the moving tube, without warpage concerns. The more force
you apply to virgin Teflon, the more "slippery" it becomes, making it an
ideal and economical substance for Crayford drive rod applications. With
the available increased force applied to the drive shaft, you can eliminate
the typical "sloppy" action notorious to previously ill-designed Crayfords
providing a more positive "rack & pinion" action, and a much higher leveraged
load handling capability for astroimaging, etc.

A Brief History of the Crayford Focuser

The Crayford Focuser was invented by English amateur John Wall of Dartford,
Kent, England in the early 1970's. His inspirational focuser was demonstrated
at the Crayford Manor House Astronomical Society and described in the
Journal of the British Astronomical Association (Feb, 1971). Also,
several examples were published in Model Engineer magazine (May, 1972).
Curiously, the Crayford focuser is not named after it's inventor, Mr. Wall,
but after the Crayford Manor House itself. Even more curious is that he never
patented the design, which rendered it unpatentable over the years because
of his existing published "prior art." Others have acquired patents for various
minor modifications to the basic Crayford design, but such patents pale in
the light of the revolutionary, original Crayford focuser implications. FYI,
an interesting article on the Crayford focuser appears in Sky & Telescope
magazine, Gleanings for ATM's (Sept, 1972, p182). Mr. Wall's original
Crayford focuser appears at right (courtesy Sky & Telescope magazine).

I would personally like to thank Mr. Wall for magnanimously donating
his invention, the Crayford focuser, to the astronomical community. The Crayford
focuser, and Mr. Wall, will live forever in the hearts [and hands] of amateur
astronomers throughout the world. It is the only focuser mechanism that offers
true zero-flexure tube movement. In my humble opinion, it is the finest,
most ingenious focusing control mechanism ever created! - PBVS